boosted class D audio power amplifier

www.DataSheet4U.com LM48510 Boosted Class D Audio Power Amplifier November 2006 LM48510 Boosted Class D Audio Power Amplifier General Description The LM48510 integrates a boost converter with a high efficiency mono, Class D audio power amplifier to provide 1.2W continuous power into an 8Ω speaker when operating on a 3.3V power supply with boost voltage (PV1) of 5.0V. When operating on a 3.3V power supply, the LM48510 is capable of driving a 4Ω speaker load at a continuous average output of 1.7W with less than 1% THD+N. The Class D amplifier is a low noise, filterless PWM architecture that eliminates the output filter, reducing external component count, board area consumption, system cost, and simplifying design. The LM48510's switching regulator is a current-mode boost converter operating at a fixed frequency of 0.6MHz. The LM48510 is designed for use in mobile phones and other portable communication devices. The high (76%) efficiency extends battery life when compared to Boosted Class AB amplifiers. The LM48510 features a low-power consumption shutdown mode. Shutdown may be enabled by driving the Shutdown pin to a logic low (GND). The gain of the Class D is externally configurable which allows independent gain control from multiple sources by summing the signals. Output short circuit and Thermal shutdown protection prevent the device from damage during fault conditions. Superior click and pop suppression eliminates audible transients during power-up and shutdown. Key Specifications ■ Quiescent Power Supply Current ■ Output Power (RL = 8Ω, THD+N ≤ 1%, VDD = 3.3V, PV1 = 5.0V) 6mA (typ) 1.2W (typ) 0.01μA (typ) ■ Shutdown Current Features ■ ■ ■ ■ ■ ■ ■ ■ Click and Pop Suppression Low 0.01μA Shutdown Current 76% Efficiency Filterless Class D 2.7V - 5.0V operation (VDD) Externally configurable gain on Class D Very fast turn on time: 17μs Independent Boost and Amplifier shutdown pins Applications ■ ■ ■ ■ ■ Mobile Phones PDAs Portable media Cameras Handheld games Typical Application 20123266 FIGURE 1. Typical LM48510 Audio Amplifier Application Circuit Boomer® is a registered trademark of National Semiconductor Corporation. © 2006 National Semiconductor Corporation 201232 www.national.com www.DataSheet4U.com LM48510 Connection Diagram LM48510SD 20123267 Top View Order Number LM48510SD See NS Package Number SDA16B LLP-14 Pin 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 DAP Name VO1 GND1 PV1 VO2 NC1 SDBOOST GND2 FB SW GND3 VDD NC2 IN+ INV1 SDAMP Ground Function Amplifier Output Amplifier Power Input Amplifier Output No Connect Boost Regulator Active Low Shutdown Signal Ground (Booster) Feedback point that connects to external resistive divider Drain of the Internal FET Switch Power Ground (Booster) Power Supply No Connect Amplifier Non-Inverting Input Amplifier Inverting Input Amplifier Power Input Amplifier Active Low Shutdown To be soldered to board for enhanced thermal dissipation. www.national.com 2 www.DataSheet4U.com LM48510 Absolute Maximum Ratings (Notes 2, 2) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage (VDD, V1) Storage Temperature Input Voltage Power Dissipation (Note 3) ESD Susceptibility (Note 4) ESD Susceptibility (Note 5) Junction Temperature 6V −65°C to +150°C −0.3V to VDD + 0.3V Internally limited 2000V 200V 150°C Thermal Resistance  θJA (SD) 37°C/W See AN-1187 'Leadless Leadframe Packaging (LLP)' Operating Ratings Temperature Range TMIN ≤ TA ≤ TMAX Supply Voltage (VDD) Supply Voltage (V1) −40°C ≤ TA ≤ +85°C 2.7V ≤ VDD ≤ 5.0V 4.5V ≤ V1 ≤ 5.5V The following specifications apply for VDD = 3.3V, PV1 = V1 = 5.0V, AV = 6dB (Ri = 150kΩ), RL = 15µH + 8Ω +15µH, fIN = 1kHz, unless otherwise specified. Limits apply for TA = 25°C. Symbol Parameter Conditions LM48510 Typical (Note 6) IDD ISD VSDIH VSDIL TWU VOS Quiescent Power Supply Current Shutdown Current Shutdown Voltage Input High Shutdown Voltage Input Low Wake-up Time Output Offset Voltage RL = 15μH + 4Ω + 15μH THD+N = 1% (max), f = 1kHz, 22kHz, BW VDD = 3.3V RL = 15μH + 8Ω + 15μH THD+N = 1% (max), f = 1kHz, 22kHz, BW VDD = 3.3V PO Output Power RL = 15μH + 4Ω + 15μH THD+N = 10% (max), f = 1kHz, 22kHz, BW VDD = 2.7V VDD = 3.3V RL = 15μH + 8Ω + 15μH THD+N = 10% (max), f = 1kHz, 22kHz, BW VDD = 2.7V VDD = 3.3V PO = 500mW, f = 1kHz, RL = 15μH + 8Ω + 15μH, VDD = 2.7V PO = 500mW, f = 1kHz, RL = 15μH + 8Ω + 15μH, VDD = 3.3V 0.07 % 0.06 % VIN = 0, RLOAD = ∞ SDAMP = SDBOOST = GND (Note 9) SD1 Boost SD2 Amplifier SD1 Boost SD2 Amplifier 17 10 6.06 0.01 Limit (Notes 7, 8) 8.75 1 0.7VDD 1.4 0.15VDD 0.4 Units (Limits) mA (max) μA (max) V (min) V (min) V (max) V (max) μs mV Electrical Characteristics VDD = 3.3V (Notes 1, 2) 1.7 W 1.2 0.9 W (min) 1.11 1.9 W W 0.98 1.55 W W THD+N Total Harmonic Distortion + Noise 3 www.national.com www.DataSheet4U.com LM48510 Symbol Parameter Conditions LM48510 Typical (Note 6) Limit (Notes 7, 8) Units (Limits) εOS Output Noise VDD = 3.3V, f = 20Hz – 20kHz Inputs to AC GND, No weighting input referred VDD = 3.3V, f = 20Hz – 20kHz Inputs to AC GND, A weighted input referred VRIPPLE = 200mVP-P Sine, fRIPPLE = = 217Hz 67 µVRMS 47 300kΩ/Ri 89 83 55 70 76 1.24 µVRMS V/V dB dB dB dB % V AV Gain PSRR Power Supply Rejection Ratio VRIPPLE = 200mVP-P Sine, fRIPPLE = = 1kHz VRIPPLE = 200mVP-P Sine, fRIPPLE = = 10kHz CMRR η VFB Common Mode Rejection Ratio Efficiency Feedback Pin Reference Voltage VRIPPLE = 1VP-P, fRIPPLE = 217Hz PO = 1W, f = 1kHz, RL = 15μH + 8Ω + 15μH, VDD = 3.3V (Note 10) Note 1: All voltages are measured with respect to the GND pin, unless otherwise specified. Note 2: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is functional, but do not guarantee specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which guarantee specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not guaranteed for parameters where no limit is given, however, the typical value is a good indication of device performance. Note 3: The maximum power dissipation must be derated at elevated temperatures and is dictated by TJMAX, θJA, and the ambient temperature, TA. The maximum allowable power dissipation is PDMAX = (TJMAX − TA) / θJA or the given in Absolute Maximum Ratings, whichever is lower. Note 4: Human body model, 100pF discharged through a 1.5kΩ resistor. Note 5: Machine Model, 220pF–240pF discharged through all pins. Note 6: Typicals are measured at 25°C and represent the parametric norm. Note 7: Limits are guaranteed to National's AOQL (Average Outgoing Quality Level). Note 8: Datasheet min/max specification limits are guaranteed by design, test, or statistical analysis. Note 9: Shutdown current is measured with components R1 and R2 removed. Note 10: Feedback pin reference voltage is measured with the Audio Amplifier disconnected from the Boost converter (the Boost converter is unloaded). www.national.com 4 www.DataSheet4U.com LM48510 Typical Performance Characteristics THD+N vs Frequency VDD = 2.7V, RL = 15μH + 4Ω + 15μH THD+N vs Frequency VDD = 2.7V, RL = 15μH + 8Ω + 15μH 20123237 20123250 THD+N vs Frequency VDD = 3.3V, RL = 15μH + 4Ω + 15μH THD+N vs Frequency VDD = 3.3V, RL = 15μH + 8Ω + 15μH 20123239 20123240 THD+N vs Output Power VDD = 2.7V, RL = 15μH + 4Ω + 15μH THD+N vs Output Power VDD = 2.7V, RL = 15μH + 8Ω + 15μH 20123241 20123251 5 www.national.com www.DataSheet4U.com LM48510 THD+N vs Output Power VDD = 3.3V, RL = 15μH + 4Ω + 15μH THD+N vs Output Power VDD = 3.3V, RL = 15μH + 8Ω + 15μH 20123243 20123244 Power Dissipation vs Output Power VDD = 2.7V Power Dissipation vs Output Power VDD = 3.3V 20123234 20123235 Power Dissipation vs Output Power VDD = 4.2V Power Supply Current vs Output Power VDD = 2.7V 20123236 20123229 www.national.com 6 www.DataSheet4U.com LM48510 Power Supply Current vs Output Power VDD = 3.3V Power Supply Current vs Output Power VDD = 4.2V 20123230 20123231 PSRR vs. Frequency VDD = 3.3V, RL = 15μH + 8Ω + 15μH CMRR vs Frequency VDD = 3.3V, RL = 15μH + 8Ω + 15μH 20123212 20123232 Supply Current vs. Supply Voltage RL = no load SW Current vs. Duty Cycle 20123245 20123233 7 www.national.com www.DataSheet4U.com LM48510 Feedback Voltage vs. Temperature Feedback Bias Current vs. Temperature 20123224 20123225 Max Duty Cycle vs. Temperature RDS(ON) vs. Temperature 20123246 20123227 RDS(ON) vs. VIN Output Power vs. Efficiency RL = 4Ω 20123228 201232c2 www.national.com 8 www.DataSheet4U.com LM48510 Output Power vs. Efficiency RL = 8Ω Boost Converter Max. Load Current vs. VDD 201232c3 20123265 9 www.national.com www.DataSheet4U.com LM48510 Application Information GENERAL AMPLIFIER FUNCTION The audio amplifier portion of LM48510 is a Class D featuring a filterless modulation scheme. The differential outputs of the device switch at 300kHz from PV1 to GND. When there is no input signal applied, the two outputs (VO1 and VO2) switch with a 50% duty cycle, with both outputs in phase. Because the outputs of the Class D are differential, the two signals cancel each other. This results in no net voltage across the speaker, thus there is no load current during an idle state, conserving power. With an input signal applied, the duty cycle (pulse width) of the Class D outputs changes. For increasing output voltages, the duty cycle of VO1 increases, while the duty cycle of VO2 decreases. For decreasing output voltages, the converse occurs, the duty cycle of VO2 increases while the d